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排序方式: 共有196条查询结果,搜索用时 62 毫秒
1.
The study of the combined effect of gamma-radiation and acid medium (pH 7.0-2.0) on DNA and RNA showed that the radiation-induced injury to nucleic acids increased with increasing concentration of H+-ions in the medium up to pH values below which protons exerted a protective action. Irradiation of native DNA in acid medium, as compared to neutral one, increased not only the number of injured bases but also the average size of the induced local defect in the secondary structure. It was shown that the proton sensitization was determined both by the number of protonated bases and by the degree of ordering the polynucleotide chain. 相似文献
2.
H. Mussauer V.L. Sukhorukov A. Haase U. Zimmermann 《The Journal of membrane biology》1999,170(2):121-133
The interaction of human red blood cells (RBCs) with diethylenetriamine-pentaacetic acid (DTPA) or its Gd-complex (Magnevist,
a widely used clinical magnetic resonance contrast agent containing free DTPA ligands) led to the following, obviously interrelated
phenomena. (i) Both compounds protected erythrocytes against electrohemolysis in isotonic solutions caused by a high-intensity
DC electric field pulse. (ii) The inhibition of electrohemolysis was observed only when cells were electropulsed in low-conductivity
solutions. (iii) The uptake of Gd-DTPA by electropulsed RBCs was relatively low. (iv) (Gd-) DTPA reduced markedly deformability
of erythrocytes, as revealed by the electrodeformation experiments using high-frequency electric fields. Taken together, the
results indicate that (Gd-) DTPA produce stiffer erythrocytes that are more resistant to electric field exposure. The observed
effects of the chelating agents on the mechanical properties and the electropermeabilization of RBCs must have an origin in
molecular changes of the bilayer or membrane-coupled cytoskeleton, which, in turn, appear to result from an alteration of
the ionic equilibrium (e.g., Ca2+ sequestration) in the vicinity of the cell membrane.
Received: 19 January 1999/Revised: 1 April 1999 相似文献
3.
A M Sukhorukov A M Ponomareva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1987,(9):18-22
The capacity of polystyrene carriers used in the enzyme immunoassay (EIA) for adsorbing 131I-labeled human serum albumin under different conditions has been studied, and the comparison of the plates manufactured by Dynatech AG (Switzerland) and by the Leningrad Works of Medical Polymers has been made. At the first stages of the reaction the antigen is separated from the carrier and the amount of the desorbed antigen depends on its initial dose and the dilution of the assayed sera. The irregular desorption of the antigen leads to misinterpretation of the results. Comparison of the polystyrene plates has shown that each plate is characterized by individual adsorption capacity, which impedes at present the standardization of EIA-based test systems. 相似文献
4.
5.
N G Nasirov B I Sukhorukov L I Shabarchina A I Petrov 《Molekuliarnaia biologiia》1991,25(4):1024-1032
The change in survival of bacteriophages with DNA of different GC-contents after their incubation in media of different acidities with subsequent neutralization was studied. It was shown that the higher the GC-content, the more sensitive is the phage to the action of H(+)-ions. Evidence is presented that the acidic inactivation of virions is not connected with the helix-coil transition of the intraphage DNA due to its protonation. The extractability of DNA from phages subjected to different concentrations of H(+)-ions with subsequent neutralization of the medium to pH 8 was determined. The changes in: transfection ability, UV-spectra, the quantity of the residual proteins, and the contents of glutamic and lysine amino acid residues in these proteins were investigated. The effect of glutamic acid on the parameters of DNA melting curves was followed for different pH values. Proceeding from the data obtained, we concluded that acidification of the medium from neutral tp pH congruent to 4 leads to formation of non-covalent DNA-protein cross-links due to interaction of the GC base pairs of DNA with glutamic and aspartic amino acid residues, whereas acidification of the medium to pH less than 4 with subsequent neutralization to pH 8 results in the formation of covalent DNA-protein cross-links of Schiff base type. The influence of non-covalent DNA-protein cross-links on the properties of DNA and their regulatory role in genome functioning are discussed. 相似文献
6.
Changes of DNA hydration provoked by protonation in the way of Na+- and H+-ions exchange, and in the way of HCl addition to Na+-DNA, were analysed by IR-spectroscopy. Water is shown not to contribute essentially to the formation and stabilization of conformations arising when DNA is protonated. The differences between hydratation of DNA protonated by different ways are in the main accounted for by alteration of the quantities of Na+ and Cl- ions forming the aqueous-salt envelope of polynucleotide. 相似文献
7.
Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences 总被引:8,自引:0,他引:8
Abundant representation of sharks in the fossil record makes this group a
superb system in which to investigate rates and patterns of molecular
evolution and to explore the strengths and weaknesses of phylogenetic
inferences from molecular data. In this report, the molecular evolution of
the cytochrome b gene in sharks is described and the information related to
results from phylogenetic analysis of the data evaluated in the light of a
phylogeny derived independently of the molecular data. Across divergent
lineages of sharks there is evidence for significant substitution rate
variation, departure from compositional equilibrium, and substantial
homoplasy; nevertheless, the signal of evolutionary history is evident in
patterns of shared transversions and amino acid replacements.
相似文献
8.
There is marked heterogeneity of nucleotide composition in mitochondrial
DNA across divergent animals. Differences in nucleotide composition
presumably reflect differences in directional nucleotide substitution for
A+T or G+C nucleotides. In mitochondrial DNA, there is A+T directional
nucleotide substitution in most (if not all) animals surveyed, and the
magnitude of directional A+T nucleotide substitution differs greatly within
and among groups. Differences in directional nucleotide substitution among
lineages of mammals can be explained by changes in metabolic physiology.
This relationship is thought to be mediated by the effect of oxygen
radicals because these toxic compounds are by-products of aerobic
metabolism and are known mutagens. Association between metabolism and
nucleotide composition provides additional evidence in favor of the
hypothesis that rates and patterns of nucleotide substitution in
mitochondrial DNA can be influenced by factors that impinge on rates of
endogenous DNA damage.
相似文献
9.
Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections 总被引:15,自引:4,他引:11
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A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules. 相似文献
10.
Sukhorukov V. S. Voronkova A. S. Litvinova N. A. Baranich T. I. Illarioshkin S. N. 《Russian Journal of Genetics》2020,56(4):402-409
Russian Journal of Genetics - The present article reviews the rapidly growing body of research on the role of mitochondrial DNA (mtDNA) in the realization of individual risk of Parkinson’s... 相似文献